PIASTA Bi-Metal Stainless Steel A2 Self Drilling Screw
PiastaTM screws are uniquely manufactured to provide upstanding corrosive resistance as well as improve productivity on construction sites. It consists of Carbon Steel Drill point and Stainless Steel body. The two materials are fused together through special patented technique to produce this Bi-metal screw.
Bi-Metal is the technique of combining 2 different types of metal, in this case, Stainless Steel and Carbon Steel, by fusion and achieving a stainless steel screw that is able to drill into steel.
Traditional methods of installing a Stainless Steel screw would require a hole to be pre-drilled and then setting the Stainless Steel screw to fasten to the base material. The requirement of a pre-drilled hole is because Austenitic Stainless Steel (like SUS304, SUS305, SUS316, SUS318) are fundamentally soft by nature and are unable to cut into any types of metal. They cannot be harden by heat treatment nor by cryogenics without compromising their corrosion resistance.
The PiastaTM screw was designed with a simple concept in mind. To be able to finish the fastening installation in 1 process. Hence a PiastaTM would need to be able to drill and cut through the base materials, tap it and fasten the covering materials.
The PiastaTM Screw derives this ability from it having a harden carbon steel drill point which drills thru the base material and at the same time tapping it to preventing any damage to its Stainless Steel body and threads.
All PiastaTM Screws are made from Austenitic Stainless Steel grade 305 and are by nature very corrosion resistant without additional anti-corrosion coating. PiastaTM screws, however, come with an additional proprietary RuspertTM coating. This RuspertTM coating is a common feature on the PiasTM range of Carbon Steel self-drilling Screws and is able to withstand 1000Hrs of Salt Spray Exposure which is equivalent to more than 10 years of normal weathering (According to Australian Standard AS3566 Class 3). This coating, in addition to providing redundant protection, has lubricative properties, which reduces setting torque and ensuring maximum thread life.
Architects and Designers, however, have raised the concern that in the event of the carbon steel portion of the PiastaTM Screw becoming corroded, what will happen to the entire system that is erected using this screw. This is addressed by the fact that during correct and proper installation of the PiastaTM Screw, the carbon steel drill point actually clears the base material and is in fact isolated from the entire system. Hence should corrosion occur, this will be confined only to the portion which has already been expelled and will not affect the integrity of the screw, the fixing nor the entire system. Some experts suggest knocking off the drill point if it is still accessible after installation.
To maintain the corrosion resistance of the head of the PiastaTM Stainless Steel Bi-metal Self-drilling screw, it will not undertake any process of case hardening. The Surface Hardness of the Head will maintain at 350 HV.
The Tensile Strength of the Austenite Stainless Steel Part of the screw will exceed values of the A2-70 being at least 700 N/mm2.
The Welding Part is designed to resist ultimate torsion and tension values of the A2-70 Stainless Steel.
The Case-Hardened Carbon Steel part of the PiastaTM Stainless Steel Bi-metal Self-drilling screw is case-hardened to values over 600 HV.
Piasta Self Drilling Screws are tested to be in conform to the Stainless Steel A2 Fasteners of the BS EN ISO 3506.